Little beast getting a saint in "trouble" (6)
I believe the answer is:
molest
'trouble' is the definition.
(both can mean to bother or harass)
'little beast getting a saint' is the wordplay.
'little beast' becomes 'mole' (mole is a kind of beast. I am not sure about the 'little' bit.).
'getting' means one lot of letters go next to another.
'a saint' becomes 'st' (abbreviation).
'mole'+'st'='MOLEST'
'in' is the link.
Can you help me to learn more?
(Other definitions for molest that I've seen before include "Accost or pester" , "Ghost" , "Disturb, interfere with" , "Harry" , "Assault in motels" .)